In general, total knee implants consist of three components: a femoral component, a tibial component, and a patellar component. Tibial components often fall into the categories of either metal-backed (modular) or all-polyethylene (also referred to as “all-poly”) tibial components. Metal-backed or modular tibial components often have a metal tray supporting a plastic modular piece that articulates with the femoral component. An all-poly tibial component, as the name implies, is a non-modular one-piece component made entirely of polyethylene plastic.
It has been shown that the long-term results of all-polyethylene tibial components have some advantages over metal-backed tibial components. For example, all-polyethylene components are often cheaper, easier to manufacture, and can exhibit better wear characteristics than metal-backed tibial components. However, in order to add to the stability of the tibial component, such as for revision cases or in cases where there is significant bone loss in the proximal tibia, it can be advantageous to include an extended metal tibial stem or peg in the implant. In many cases, the attachment of such a metal component directly to a polyethylene component can be difficult and may result in unsatisfactory attachment conditions. Thus, it has been known to use a tibial component that includes a polyethylene or other plastic portion with an attached metal backing to allow for attachment of an extended metal tibial stem or peg to the metal backing portion of the tibial component. However, there is a need to provide a knee implant assembly that allows a metal peg to be attached to an all-poly tibial component, thus offering the advantages of both metal-backed and all-poly tibial components.